1. Field of the Invention
The present invention relates to apparatus and processes for the fabrication of a microelectronic device. In particular, the present invention relates to a fabrication technology that encapsulates at least one microelectronic die and provides a laminated interconnection layer for achieving electronic contact therewith.
2. State of the Art
Higher performance, lower cost, increased miniaturization of integrated circuit components, and greater packaging density of integrated circuits are ongoing goals of the computer industry. As these goals are achieved, microelectronic dice become smaller. Of course, the goal of greater packaging density requires that the entire microelectronic die package be equal to or only slightly larger (about 10% to 30%) than the size of the microelectronic die itself. Such microelectronic die packaging is called a “chip scale packaging” or “CSP”.
As shown in FIG. 35, true CSP involves fabricating build-up layers directly on an active surface 404 of a microelectronic die 402. The build-up layers may include a dielectric layer 406 disposed on the microelectronic die active surface 404. Conductive traces 408 may be formed on the dielectric layer 406, wherein a portion of each conductive trace 408 contacts at least one contact 412 on the active surface 404. External contacts, such as solder balls or conductive pins for contact with an external component (not shown), may be fabricated to electrically contact at least one conductive trace 408. FIG. 35 illustrates the external contacts as solder balls 414, which are surrounded by a solder mask material 416 on the dielectric layer 406. However, in such true CSP, the surface area provided by the microelectronic die active surface 404 generally does not provide enough surface for all of the external contacts needed to contact the external component (not shown) for certain types of microelectronic dice (e.g., logic).
Additional surface area can be provided through the use of an interposer, such as a substrate (substantially rigid material) or a flex component (substantially flexible material). FIG. 36 illustrates a substrate interposer 422 having a microelectronic die 424 attached to and in electrical contact with a first surface 426 of the substrate interposer 422 through small solder balls 428. The small solder balls 428 extend between contacts 432 on the microelectronic die 424 and conductive traces 434 on the substrate interposer first surface 426. The conductive traces 434 are in discrete electrical contact with bond pads 436 on a second surface 438 of the substrate interposer 422 through vias 442 that extend through the substrate interposer 422. External contacts 444 (shown as solder balls) are formed on the bond pads 436. The external contacts 444 are utilized to achieve electrical communication between the microelectronic die 424 and an external electrical system (not shown).
The use of the substrate interposer 422 requires a number of processing steps. These processing steps increase the cost of the package. Additionally, even the use of the small solder balls 428 presents crowding problems which can result in shorting between the small solder balls 428 and can present difficulties in inserting underfill material between the microelectronic die 424 and the substrate interposer 422 to prevent contamination and provide mechanical stability. Furthermore, current packages may not meet power delivery requirements for future microelectronic dice 424 due to thickness of the substrate interposer 422, which causes land-side capacitors to have too high an inductance.
FIG. 37 illustrates a flex component interposer 452 wherein an active surface 454 of a microelectronic die 456 is attached to a first surface 458 of the flex component interposer 452 with a layer of adhesive 462. The microelectronic die 456 is encapsulated in an encapsulation material 464. Openings are formed in the flex component interposer 452 by laser ablation through the flex component interposer 452 to contacts 466 on the microelectronic die active surface 454 and to selected metal pads 468 residing within the flex component interposer 452. A conductive material layer is formed over a second surface 472 of the flex component interposer 452 and in the openings. The conductive material layer 482 is patterned with standard photomask/etch processes to form conductive vias 474 and conductive traces 476. External contacts are formed on the conductive traces 476 (shown as solder balls 478 surrounded by a solder mask material 482 proximate the conductive traces 476).
The use of a flex component interposer 452 requires gluing material layers which form the flex component interposer 452 and requires gluing the flex component interposer 452 to the microelectronic die 456. These gluing processes are relatively difficult and increase the cost of the package. Furthermore, the resulting packages have been found to have poor reliability.
Therefore, it would be advantageous to develop new apparatus and techniques to provide additional surface area to form traces for use in CSP applications, which overcomes the above-discussed problems.